[en] In this paper, we present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities M_i [z = 2] < -20.5 (in a ΛCDM cosmology with H_0 = 70 km s"-"1 Mpc"-"1, Ω_M = 0.3, and Ω_Λ = 0.7), and either display at least one emission line with a full width at half maximum (FWHM) larger than 500 km s"-"1 or, if not, have interesting/complex absorption features. The catalog also includes previously known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 297 301 quasars (272 026 are new discoveries since the beginning of SDSS-III) detected over 9376 deg"2 with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with z > 2.15 (184 101, of which 167 742 are new discoveries) is about an order of magnitude greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C iv, C iii], Mg ii). The catalog identifies 29 580 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and Palomar Transient Factory multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3600–10 500 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Catalog Archive Server. Finally, we also provide a supplemental list of an additional 4841 quasars that have been identified serendipitously outside of the superset defined to derive the main quasar catalog.

[en] The flat spectrum radio quasar (FSRQ) PKS 0208–512 underwent three outbursts at the optical-near-infrared (OIR) wavelengths during 2008-2011. The second OIR outburst did not have a γ-ray counterpart despite being comparable in brightness and temporal extent to the other two. We model the time variable spectral energy distribution of PKS 0208–512 during those three flaring episodes with leptonic models to investigate the physical mechanism that can produce this anomalous flare. We show that the redder-when-brighter spectral trend in the OIR bands can be explained by the superposition of a fixed thermal component from the accretion disk and a synchrotron component of fixed shape and variable normalization. We estimate the accretion disk luminosity at L_d ≅ 8 × 10⁴⁵ erg s^–1. Using the observed variability timescale in the OIR band t_var,obs ≅ 2 days and the X-ray luminosity L_X ≅ 3.5 × 10⁴⁵ erg s^–1, we are able to constrain the location of the emitting region to distance scales that are broadly comparable with the dusty torus. We show that variations in the Compton dominance parameter by a factor of ∼4—which may result in the anomalous outburst—can be relatively easily accounted for by moderate variations in the magnetic field strength or the location of the emission region. Since such variations appear to be rare among FSRQs, we propose that most γ-ray/OIR flares in these objects are produced in jet regions where the magnetic field and external photon fields vary similarly with distance along the jet, e.g., u_B^'∝u_ext^'∝r^-2.

[en] We report the discovery of a quasar pair at z = 5 separated by 21″. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the Canada–France–Hawaii Telescope (CFHT) Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the hypothesis that they are gravitationally lensed images of a single quasar. Both quasars are surprisingly bright given their proximity (a projected separation of ∼135 kpc), with i = 19.4 and i = 21.4. Previous measurements of the luminosity function demonstrate that luminous quasars are extremely rare at z = 5; the existence of this pair suggests that quasars have strong small-scale clustering at high redshift. Assuming a real-space correlation function of the form ξ(r) ∝ (r/r_0)"−"2, this discovery implies a correlation length of r_0 ≳ 20h"−"1 Mpc, consistent with a rapid strengthening of quasar clustering at high redshift as seen in previous observations and predicted by theoretical models where feedback effects are inefficient at shutting down black hole growth at high redshift

[en] Recent work on quasar clustering suggests a degeneracy in the halo occupation distribution constrained from two-point correlation functions. To break this degeneracy, we make the first empirical measurement of the mean occupation function (MOF) of quasars at z ∼ 0.2 by matching quasar positions with groups and clusters identified in the MaxBCG sample. We fit two models to the MOF, a power law and a four-parameter model. The number distribution of quasars in host halos is close to Poisson, and the slopes of the MOF obtained from our best-fit models (for the power-law case) favor an MOF that monotonically increases with halo mass. The best-fit slopes are 0.53 ± 0.04 and 1.03 ± 1.12 for the power-law model and the four-parameter model, respectively. We measure the radial distribution of quasars within dark matter halos and find it to be adequately described by a power law with a slope –2.3 ± 0.4. We measure the conditional luminosity function (CLF) of quasars and show that there is no evidence that quasar luminosity depends on host halo mass, similar to the inferences drawn from clustering measurements. We also measure the conditional black hole mass function (CMF) of our quasars. Although the results are consistent with no dependence on halo mass, we observe a slight indication of downsizing of the black hole mass function. The lack of halo mass dependence in the CLF and CMF shows that quasars residing in galaxy clusters have characteristic luminosity and black hole mass scales.

[en] Standard maximum-likelihood estimators for binary-star and exoplanet eccentricities are biased high, in the sense that the estimated eccentricity tends to be larger than the true eccentricity. As with most non-trivial observables, a simple histogram of estimated eccentricities is not a good estimate of the true eccentricity distribution. Here, we develop and test a hierarchical probabilistic method for performing the relevant meta-analysis, that is, inferring the true eccentricity distribution, taking as input the likelihood functions for the individual star eccentricities, or samplings of the posterior probability distributions for the eccentricities (under a given, uninformative prior). The method is a simple implementation of a hierarchical Bayesian model; it can also be seen as a kind of heteroscedastic deconvolution. It can be applied to any quantity measured with finite precision-other orbital parameters, or indeed any astronomical measurements of any kind, including magnitudes, distances, or photometric redshifts-so long as the measurements have been communicated as a likelihood function or a posterior sampling.

[en] ABSTRACT We examine multiple active galactic nucleus (AGN) systems (triples and quadruples, in particular) in the MassiveBlackII simulation over a redshift range of 0.06 ≲ z ≲ 4. We identify AGN systems (with bolometric luminosity $L_{\mathrm{b}\mathrm{o}\mathrm{l}}><!--\; >\; -->{10}^{42}{\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{s}}^{-<!--\; ???\; -->1}$) at different scales (defined by the maximum distance between member AGNs) to determine the AGN multiplicity functions. This is defined as the volume/surface density of AGN systems per unit richness R, the number of AGNs in a system. We find that gravitationally bound multiple AGN systems tend to populate scales of $\lesssim <!--\; ???\; -->0.7\mathrm{c}\mathrm{M}\mathrm{p}\mathrm{c}{h}^{-<!--\; ???\; -->1}$; this corresponds to angular separations of ≲100 arcsec and a line-of-sight velocity difference $\lesssim <!--\; ???\; -->200{\mathrm{k}\mathrm{m}\mathrm{s}}^{-<!--\; ???\; -->1}$. The simulation contains ∼10 and ∼100 triples/quadruples per deg2 up to depths of DESI (g ≲ 24) and LSST (g ≲ 26) imaging, respectively; at least $20\mathrm{p}\mathrm{e}\mathrm{r}\mathrm{c}\mathrm{e}\mathrm{n}\mathrm{t}$ of these should be detectable in spectroscopic surveys. The simulated quasar ($L_{\mathrm{b}\mathrm{o}\mathrm{l}}><!--\; >\; -->{10}^{44}{\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{s}}^{-<!--\; ???\; -->1}$) triples and quadruples predominantly exist at 1.5 ≲ z ≲ 3. Their members have black hole masses ${10}^{6.5}\lesssim <!--\; ???\; -->M_{\mathrm{b}\mathrm{h}}\lesssim <!--\; ???\; -->{10}^9{\mathrm{M}}_{\odot <!--\; ???\; -->}{h}^{-<!--\; ???\; -->1}$ and live in separate (one central and multiple satellite) galaxies with stellar masses ${10}^{10}\lesssim <!--\; ???\; -->M_{\ast <!--\; ???\; -->}\lesssim <!--\; ???\; -->{10}^{12}{\mathrm{M}}_{\odot <!--\; ???\; -->}{h}^{-<!--\; ???\; -->1}$. They live in the most massive haloes (e.g. $\sim <!--\; ???\; -->{10}^{13}{\mathrm{M}}_{\odot <!--\; ???\; -->}{h}^{-<!--\; ???\; -->1}$ at z = 2.5; $\sim <!--\; ???\; -->{10}^{14}{\mathrm{M}}_{\odot <!--\; ???\; -->}{h}^{-<!--\; ???\; -->1}$ at z = 1) in the simulation. Their detections provide an exciting prospect for understanding massive black hole growth and their merger rates in galaxies in the era of multimessenger astronomy.

[en] Clustering measurements of obscured and unobscured quasars show that obscured quasars reside in more massive dark matter halos than their unobscured counterparts. These results are inconsistent with simple unified (torus) scenarios but might be explained by models in which the distribution of obscuring material depends on Eddington ratio or galaxy stellar mass. We test these possibilities by constructing simple physical models to compare to observed active galactic nucleus populations. We find that previously observed relationships between obscuration and Eddington ratio or stellar mass are not sufficient to reproduce the observed quasar clustering results ($⟨<!--\; ???\; -->\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}}/M_{\odot <!--\; ???\; -->}⟩<!--\; ???\; -->={12.94}_{-<!--\; ???\; -->0.11}^{+0.10}$ and $⟨<!--\; ???\; -->\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}}/M_{\odot <!--\; ???\; -->}⟩<!--\; ???\; -->={12.49}_{-<!--\; ???\; -->0.08}^{+0.08}$ for obscured and unobscured populations, respectively) while maintaining the observed fraction of obscured quasars (30%–65%). This work suggests that evolutionary models, in which obscuration evolves on the typical timescale for black hole growth, are necessary to understand the observed clustering of mid-IR-selected quasars.

[en] We present spatially resolved long-slit spectroscopy from the Southern African Large Telescope to examine the spatial extent of the narrow-line regions (NLRs) of a sample of eight luminous obscured quasars at 0.10 < z < 0.43. Our results are consistent with an observed shallow slope in the relationship between NLR size and L_[OIII], which has been interpreted to indicate that NLR size is limited by the density and ionization state of the NLR gas rather than the availability of ionizing photons. We also explore how the NLR size scales with a more direct measure of instantaneous active galactic nucleus power using mid-IR photometry from the Wide Field Infrared Explorer, which probes warm to hot dust near the central black hole and so, unlike [O III], does not depend on the properties of the NLR. Using our results as well as samples from the literature, we obtain a power-law relationship between NLR size and L_8μm that is significantly steeper than that observed for NLR size and L_[OIII]. We find that the size of the NLR goes approximately as L^1/2_8μm, as expected from the simple scenario of constant-density clouds illuminated by a central ionizing source. We further see tentative evidence for a flattening of the relationship between NLR size and L_8μm at the high-luminosity end, and propose that we are seeing a limiting NLR size of 10-20 kpc, beyond which the availability of gas to ionize becomes too low. We find that L_[OIII]∼L_8μm^1.4, consistent with a picture in which the L_[OIII] is dependent on the volume of the NLR. These results indicate that high-luminosity quasars have a strong effect in ionizing the available gas in a galaxy

[en] As a natural consequence of galaxy mergers, binary active galactic nuclei (AGNs) should be commonplace. Nevertheless, observational confirmations are rare, especially for binaries with separations less than 10 kpc. Such a system may show two sets of narrow emission lines in a single spectrum owing to the orbital motion of the binary. We have obtained high-resolution near-infrared images of 50 double-peaked [O III]λ5007 AGNs with the Keck II laser guide star adaptive optics system. The Sloan Digital Sky Survey sample is compiled from the literature and consists of 17 type-1 AGNs between 0.18 < z < 0.56 and 33 type-2 AGNs between 0.03 < z < 0.24. The new images reveal eight type-1 and eight type-2 sources that are apparently undergoing mergers. These are strong candidates of kpc-scale binary AGNs because they show multiple components separated between 0.6 and 12 kpc and often disturbed morphologies. Because most of the type-1s are at higher redshifts than the type-2s, the higher merger fraction of type-1s (47% ± 20%) compared to that of type-2s (24% ± 10%) can be attributed to the general evolution of galaxy merger fraction with redshift. Furthermore, we show that AGN mergers are outliers of the M_BH-σ_* relation because of overestimated stellar velocity dispersions, illustrating the importance of removing mergers from the samples defining the M_BH-σ_* relations. Finally, we find that the emission-line properties are indistinguishable for spatially resolved and unresolved sources, emphasizing that scenarios involving a single AGN can produce the same double-peaked line profiles and they account for at least 70% of the double-peaked [O III] AGNs.

[en] We present the results of an optical spectroscopic survey of a sample of 40 candidate obscured quasars identified on the basis of their mid-infrared emission detected by the Wide-Field Infrared Survey Explorer (WISE). Optical spectra for this survey were obtained using the Robert Stobie Spectrograph on the Southern African Large Telescope. Our sample was selected with WISE colors characteristic of active galactic nuclei (AGNs), as well as red optical to mid-IR colors indicating that the optical/UV AGN continuum is obscured by dust. We obtain secure redshifts for the majority of the objects that comprise our sample (35/40), and find that sources that are bright in the WISE W4 (22 μm) band are typically at moderate redshift ((z) = 0.35) while sources fainter in W4 are at higher redshifts ((z) = 0.73). The majority of the sources have narrow emission lines with optical colors and emission line ratios of our WISE-selected sources that are consistent with the locus of AGN on the rest-frame g – z color versus [Ne III] λ3869/[O II] λλ3726+3729 line ratio diagnostic diagram. We also use empirical AGN and galaxy templates to model the spectral energy distributions (SEDs) for the objects in our sample, and find that while there is significant variation in the observed SEDs for these objects, the majority require a strong AGN component. Finally, we use the results from our analysis of the optical spectra and the SEDs to compare our selection criteria to alternate criteria presented in the literature. These results verify the efficacy of selecting luminous obscured AGNs based on their WISE colors.